Okla. Stat. tit. 17, § 17-13: Admission of evidence

The Corporation Commission shall in the trial of cases and all

special proceedings and hearings admit in evidence only such balance

sheets, operating statements and other financial exhibits and

schedules as shall have been compiled and authenticated by the

treasurer or other regularly acting financial officer or employee of

such person, firm, association or corporation as may be a party to

the proceeding, action or cause pending before or being tried by

said Commission; provided, that if otherwise relevant and

admissible, reports of audit, balance sheets, operating statements

and financial exhibits and schedules prepared by employees of said

Commission, employees of the Office of the Attorney General, and by

public accountants as defined in Section 15.1 et seq. of Title 59 of

the Oklahoma Statutes or certified public accountants under the laws

of the state, shall be admissible and accepted in evidence in all

cases.